docs: document empty-matrix return value

PR-URL: #13396
Reviewed-by: Athan Reines <kgryte@gmail.com>

Author: Planeshifter

lib/node_modules/@stdlib/lapack/base/iladlr/lib/iladlr.js

@@ -33,6 +33,10 @@ var base = require( './base.js' );
 /**
 * Returns the index of the last non-zero row in a matrix `A`.
 *
+* ## Notes
+*
+* -   If provided an empty matrix or a matrix containing only zeros, the function returns `-1` (i.e., an invalid index).
+*
 * @param {string} order - storage layout
 * @param {PositiveInteger} M - number of rows in `A`
 * @param {PositiveInteger} N - number of columns in `A`